Dishwasher with multiple treating chambers

ABSTRACT

A method of operating a dishwasher having multiple wash chambers, with each wash chamber executing a different cycle of operation, and liquid from one chamber may be reused in the other chamber.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.13/185,546, filed Jul. 19, 2011, which application is a continuation ofU.S. patent application Ser. No. 12/959,651, filed Dec. 3, 2010, nowU.S. Pat. No. 8,043,437 both of which are incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION

Dishwashers can include multiple compartments in the form of multipledrawers or pull-out compartments slidably mounted in a cabinet. Eachcompartment can include a tub defining a treating chamber. Typically, adish rack is provided in each treating chamber to support utensilsduring a treating cycle of operation. Treating liquid may be provided toeach of the treating chambers to treat utensils. The treating liquid maybe, for example, water, treating chemistry, or a mixture of water andtreating chemistry. Some dishwashers may be provided one or more sensorsto monitor the soil load in the treating liquid.

BRIEF DESCRIPTION OF THE INVENTION

A method of operating a dishwasher having multiple treating chamberscomprises determining which of the multiple treating chambers has thelightest soil load to define a treating chamber with the lightest soilload, implementing a wash cycle selected for the treating chamber withthe lightest soil load by supplying a charge of treating liquid to thetreating chamber with the lightest load, supplying the treating liquidfrom the treating chamber with the lightest soil load to another one ofthe multiple treating chambers, and implementing another wash cycleselected for the another one of the treating chamber using the treatingliquid from the treating chamber with the lightest soil load.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic, front view of a first exemplary dishwasher havingmultiple treating chambers.

FIG. 2 is a flow chart showing a method of operating the dishwasher ofFIG. 1 according to a first embodiment of the invention.

FIG. 3 is a flow chart showing a method of operating the dishwasher ofFIG. 1 according to a second embodiment of the invention.

FIG. 4 is a schematic, perspective view of a second exemplary dishwasherhaving multiple treating chambers in the form of a drawer-typedishwasher.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention is generally directed toward sharing treating liquid in adishwasher having multiple treating chambers. One aspect of theinvention is to transfer treating liquid from one treating chamber toanother treating chamber to share the treating liquid between multipletreating chambers and conserve resources. Initially, the treatingchamber with the lightest soil load may be determined. The treatingliquid may be provided to this treating chamber for implementing a washstep of a wash cycle. When the wash step is complete, the treatingliquid may be transferred to another treating chamber having heaviersoil load for a use in a wash step of a wash cycle. Additionally, it isnoted that an excess dose of treating chemistry may cause damage to theutensils in a treating chamber during a wash cycle. The inventionaddresses problems associated with sharing treating liquid betweenmultiple treating chambers to minimize the use of treating chemistry andwater, while maintaining a quality of treatment, and controlling thedose of treating chemistry to prevent any damage to the utensils. Forpurposes of this description, the term “utensil(s)” is intended to begeneric to any item, single or plural, that may be treated in adishwasher, including, without limitation; dishes, plates, pots, bowls,pans, glassware, and silverware.

FIG. 1 is a schematic, front view of a first exemplary dishwasher 10having multiple treating chambers. As illustrated, the dishwasher 10 maycomprise a cabinet 12 defining an interior 14, which is accessiblethrough a moveable cover, such as a door or drawer (not shown). Thecabinet 12 may comprise a chassis or frame to which panels may bemounted. For built-in dishwashers, the outer panels are typically notneeded. Multiple wash tubs 16 may be provided within the interior 14 ofthe cabinet 12. As illustrated, two wash tubs 16 are provided in aside-by-side arrangement. Each wash tub 16 may at least partially definea treating chamber 18 that receives and treats utensils according to acycle of operation, often referred to a wash cycle. Each wash tub 16 mayhave optionally an open face (not shown) that is closed by the cover.Alternatively, each wash tub 16 may be provided with an individual coverfor closing the open face. Each wash tub 16 may be fluidly connected toeach other through an exchange conduit 20 and control valves 22.

Although the dishwasher 10 may be configured to have two wash tubs 16inside a single cabinet 12, it is noted that many other configurationsmay be also possible. For example, the dishwasher 10 may include twoseparate cabinets 12, each having a single wash tub 16. It is alsocontemplated that more than two wash tubs 16 can be provided for thedishwasher 10. It is also contemplated that wash tubs 16 may bepositioned in a side-by-side configuration, as illustrated, a stackedconfiguration, such as a drawer-type dishwasher, or mixture thereof.Regardless of the number and orientation of the wash tubs 16, the washtubs 16 will be fluidly connected to each other.

As illustrated, the wash tubs 16 and associated components operablycoupled to the wash tubs 16 have similar structures and configurations,either as a whole or on a component basis. Therefore, only one of thewash tubs 16 and associated components will be described unlessotherwise required, with the understanding that the description appliesto both wash tubs 16.

One or more utensil rack(s) 28 may be provided in the treating chamber18 for supporting various objects, such as utensils and the like, to beexposed to a wash cycle. The utensil rack 28 may be mounted for slidingmovement into and out of the treating chamber 18 through the openingclosed by the cover (not shown).

A liquid supply system may be provided for supplying liquid to thetreating chamber 18 as part of a wash cycle for washing any utensilswithin the utensil rack 18. The liquid supply system may include one ormore liquid sprayers, which is illustrated in the form of a spray armassembly 32 that is provided within the treating chamber 18. The sprayarm assembly 32 is positioned in the wash tub 16 beneath the utensilrack 28 and configured to rotate in the treating chamber 18 to generatea spray of treating liquid in a generally upward direction, over aportion of the interior of the respective treating chamber 18, typicallydirected to treat utensils located in the utensil rack 28. While thespray arm assembly 32 is illustrated as a rotating spray arm, the sprayarm assembly 32 can be of any structure and configuration, such as fixedspray heads. Additional spray arms or nozzles can also be provided.

The liquid supply system further comprises a lower tub region or sump 36which collects treating liquid sprayed within the treating chamber 18.The sump 36 is illustrated as being formed with or affixed to a lowerportion of the wash tub 16 to collect treating liquid that may besupplied into or circulated in the wash tub 16 during, before or after acycle of operation. Alternatively, the sump 36 may be remote from thewash tub 16 and fluidly coupled to the wash tub 16 by suitable fluidconduits.

The liquid supply system further comprises a pump assembly 26 fluidlycoupled to the sump 36 through an inlet 37 to receive liquid from thesump 36. The pump assembly 26 may have both a recirculation pump 38 anda drain pump 40. The recirculation pump 38 fluidly couples the sump 36to the spray arm assembly 32 through a spray arm supply conduit 42 suchthat the recirculation pump 38 can selectively pump treating liquid thatcollects in the sump 36 to the spray arm assembly 32. In this way, therecirculation pump 38 can redistribute treating liquid collecting in thesump 36 through the spray arm assembly 32 into the treating chamber 18,where the liquid naturally flows back under the force of gravity to thesump 36 for recirculation or drainage, depending on the phase or step ofthe wash cycle. The drain pump 40 fluidly couples the sump 36 to a drainconduit 44 and may be used to drain treating liquid from the sump 36,through the drain conduit 44, and out of the dishwasher 10, such as to ahousehold drain, a sewer line, or the like.

The spray arm supply conduit 42 may be fluidly coupled to the exchangeconduit 20 through a control valve 22 which selectively places the sump36 in fluid communication with the pump assembly 26 or with the exchangeconduit 20.

Treating liquid from one treating chamber 18 can be transferred to theother treating chamber 18 by controlling the control valves 22. Forexample, the control valves 22 and the operation of one of therecirculation pumps 38 may be configured to direct the flow to thesprayer in the other chamber to transfer the fluid between chambers 16.In one embodiment, the control valves 22 may be a single valve.

A chemistry dispenser 48 may be provided for dispensing a treatingchemistry, which can include detergent and/or rinse aid, into thetreating chamber 18. As illustrated, the chemistry dispenser may belocated on a side wall of the wash tub 16. Alternatively, the chemistrydispenser 48 may be located anywhere inside the wash tub 16 or in thecover (not shown). It will be understood that depending on the type ofdishwasher and the type of treating chemistry used, the chemistrydispenser 48 may be incorporated into one dispensing mechanism. Thechemistry dispenser 48 may be of a single-use dispenser, which stores asingle dose of treating chemistry, or a bulk dispenser, which storesmultiple doses of treating chemistry. In the case of bulk dispensing,the treating chemistry can be selectively dispensed into the treatingchamber 18 in a regulated quantity and at a predetermined time ormultiple times during a cycle of operation. A common chemistry dispenseris a single-use dispenser mounted to an inside surface of a door or afront wall of a drawer. The dispenser has a door that automaticallyopens during a washing phase.

The dishwasher 10 further comprises a heater 52 that may be locatedwithin the sump 36 to selectively heat liquid collected in the sump 36.The heater 52 may be an immersion heater in direct contact with treatingliquid in the sump 36 to provide the liquid with predetermined heatenergy. The heater 52 may also be employed to heat air in the treatingchamber 18, such as for a heated drying step of a cycle of operation.Alternately, a separate heater (not shown) can be provided for heatingair. A temperature sensor such as a thermistor 54 may also be positionedin the sump 36 to provide an output signal that is indicative of thetemperature of any fluid, including treating liquid or air, in the sump36. A pH sensor 56 may also be positioned in the sump 36 to provide anoutput signal indicative of the pH of the treating liquid in the sump36. A turbidity sensor 58 may also be positioned in the sump 36 toprovide an output signal that is indicative of the turbidity of thetreating liquid in the sump 36.

The dishwasher 10 further comprises a controller 60 for implementing oneor more cycles of operation. The dishwasher 10 may be preprogrammed witha number of different cleaning cycles from which a user may select onecleaning cycle to clean a load of utensils. Examples of cleaning cyclesinclude normal, light/china, heavy/pots and pans, and rinse only. Asillustrated, a single controller 60 may be provided for both treatingchambers 18, and may be operably coupled to various components of thedishwasher 10 to implement a wash cycle in one or both of the treatingchambers 18. For example, the controller 60 may be coupled with therecirculation pumps 38 for circulation of liquid in the wash tubs 16 andthe drain pumps 40 for drainage of liquid from the wash tubs 16. Thecontroller 60 may also be coupled with the heater 52 to heat the liquidand/or air depending on the step being performed in the cycle ofoperation. The controller 60 may also be coupled to the chemistrydispensers 48 to dispense a treating chemistry during a wash step and/orrinse step of a cycle of operation. The controller 60 may also becoupled to the thermistor 54, pH sensor 56, and a turbidity sensor 58 toeither control these sensors and/or receive their output signal for usein controlling the components of the dishwasher 10. The controller 60may also be coupled to the control valves 22 for selectivelytransferring treating liquid from one treating chamber 18 to anothertreating chamber 18.

A control panel or user interface 62 for use in selecting a wash cyclecan be provided on the dishwasher 10 and coupled to the controller 60.The user interface 62 may receive input from a user for theimplementation of a wash cycle and provide the user with informationregarding the wash cycle. In this way, the controller 60 can implement awash cycle selected by a user according to any options selected by theuser and provide related information to the user. The user interface 62may include operational controls such as dials, lights, knobs, levers,buttons, switches, and displays enabling the user to input commands tothe controller 60 and receive information about the selected treatmentcycle. The user interface 62 may be used to select a treatment cycle totreat a load of utensils. Alternatively, the treatment cycle may beautomatically selected by the controller 60 based on the soil levelssensed by any sensors in the dishwasher 10 to optimize the treatmentperformance of the dishwasher 10 for a particular load of utensils.

The controller 60 may be provided with a memory 66 and a centralprocessing unit (CPU) 64. The memory 66 may be used for storing controlsoftware that may be executed by the CPU 64 in completing a cycle ofoperation using one or both treating chambers 18 of the dishwasher 10and any additional software. For example, the memory 66 may store one ormore pre-programmed cycles of operation that may be selected by a userand completed in one of the treating chambers 18. A cycle of operationfor the treating chambers 18 may include one or more of the followingsteps: a wash step, a rinse step, and a drying step. The wash step mayfurther include a pre-wash step and a main wash step. The rinse step mayalso include multiple steps such as one or more additional rinsing stepsperformed in addition to a first rinsing. The amounts of water and/orrinse aid used during each of the multiple rinse steps may be varied.The drying step may have a non-heated drying step (so called “aironly”), a heated drying step or a combination thereof. These multiplesteps may also be performed within the treating chambers 18 in anydesired combination.

FIG. 2 is a flow chart showing a method 200 of operating the dishwasherof FIG. 1 according to an embodiment of the invention. The sequence ofsteps depicted is for illustrative purposes only, and is not meant tolimit the method 200 in any way as it is understood that the steps mayproceed in a different logical order or additional or intervening stepsmay be included without detracting from the invention. The method 200may be implemented independently or as a part of a wash cycle, such as apre-wash, wash, rinse, or dry step. The method 200 assumes that utensilsare provided in each treating chamber 18 of the dishwasher 10 fortreatment, and that the dishwasher 10 has two treating chambers 18.However, the method 200 may be implemented by a dishwasher having aconfiguration other than the configuration shown in FIG. 1. The method200 also assumes that the wash cycles for the two treating chambers 18are configured to use the same treating chemistry.

At 202, a determination is made as to which treating chamber 18 has thelightest soil load. The soil load is an amount or level of soil for aload of utensils within a treating chamber 18. Therefore, the treatingchamber 18 with the lightest soil load will be the treating chamber withthe load of utensils having the least amount or lowest level of soil.Determining the treating chamber 18 with the lightest soil load may beaccomplished in different ways. In one example, the determination may bea user input. The user may visually evaluate and/or compare the load ofutensils in each treating chamber 18 when the user places the utensilsin each treating chamber 18. The user may then manually designate onetreating chamber having the lighter soil load through the user interface62. It can also be done inferentially by the controller based on thecycle of operation selected by the user for each treating chamber. Forexample, the controller may have a table of data ranking, based onanticipated soil load levels, the different cycles of operation that theuser may select and automatically assign as the lighter load chamber,the chamber having the cycle with the anticipated lighter soil load. Forexample, if the cycle for one chamber is a Heavy Duty cycle and theother is a Normal cycle, it will be anticipated that the chamber withthe Normal cycle will be have the lighter soil load. Similarly, ifNormal and China cycles are selected, it is anticipated that the chamberwith the China cycle will have the lighter soil load. Alternatively,after placing the utensils in each treating chamber 18, the soil loadsmay be sensed using any suitable method. For example, an optical sensor,such as a camera sensor may monitor the arrangement and location of theutensils in each wash tub 16 to determine which of the wash tub 16 hasthe lightest soil load based on the number and types of utensils.Alternatively, the camera sensor may be used to determine the amount ofsoils on the utensils in addition to the type and amount of utensils.Liquid may also be sprayed within each of the treating chambers and thecorresponding turbidity of the liquid sensed and compared to determinewhich of the chambers has the lightest soil load. For the purposes ofthe description of the method 200, the treating chamber 18 has thelightest soil load will be referred to as the first treating chamber 18and the other treating chamber 18 will be referred to as the secondtreating chamber 18.

At 204, a wash step of the wash cycle may be implemented in the firsttreating chamber 18. The wash step includes supplying treating liquid tothe treating chamber 18. The treating liquid can be sprayed onto theutensils in the utensil rack 28 from the spray arm assembly 32. Thetreating liquid may be recirculated through the treating chamber 18 oneor more times by the recirculation pump 38. Treating chemistry canoptionally be dispensed from the chemistry dispenser 48. During 204, thewash cycle in the second treating chamber 18 may not be initiated untilthe wash cycle in the first treating chamber 18 is complete.

At 206, the usefulness of the treating liquid in the first treatingchamber 18 may be checked. As used herein, the usefulness may includethe amount of available detergent, available enzyme load, pH, soil load,turbidity, and temperature profile. This may be done after the wash stepin the first treating chamber 18 is complete. The usefulness may bemonitored using sensors provided in the dishwasher 10, such as the pHsensor 56, the turbidity sensor 58, or another chemical sensor (notshown). For example, the pH sensor 56 may monitor the pH of the treatingliquid in the first treating chamber 18. It is noted that the pH oftreating liquid having treating chemistry tends to decrease as thetreating liquid is repeatedly recirculated, and the treating liquid maynot be effective in removing soils when the pH of the treating liquiddrops down below a predetermined pH threshold.

Similar to the usefulness of the treating liquid, a cleaning action ofthe treating liquid may be determined. Cleaning action could be measuredor estimated by determining the type and concentration of the detergentused in the treating liquid, the softness of the water used in thetreating liquid, the amount of soils present in the treating liquid, aswell as the temperature profile of the treating liquid. The cleaningaction may also be determined by a look-up table having at least one ofconcentration, temperature, pH of the treating liquid, water hardnessand soil level, which may be sensed by a suitable sensor. In someinstances, the amount of cleaning action may be great enough toundesirably alter, temporarily or permanently, a physical characteristicof the utensils. For example, it is known that glasses are prone tochemical etching when in the presence of high temperature, high pH, andhigh concentrations of builder chemistry, with one example of a builderchemistry being phosphate. A lookup table of cleaning action based onthe above factors could be used to determine if the cleaning action isbelow a threshold that would make it safe to use in a given wash step.In general, there is a proportional relationship for cleaning action anddetergent concentration, treating liquid temperature, and pH. Ingeneral, there is an inverse relationship for cleaning action and waterhardness and soil levels

The output signal from the pH sensor 56 and/or the turbidity sensor 58may be sent to the controller 60, where the output signal may becompared to reference data stored in the memory 66, and thedetermination as to the usefulness of the treating liquid may be made at208. The reference data can include values or ranges of valuescorresponding to pH and turbidity that are considered sufficient for usein another wash cycle and/or values or ranges of values corresponding topH and turbidity that are considered insufficient for use in anotherwash cycle.

If the usefulness of the treating liquid is determined to besufficiently useful at 208, the treating liquid may be transferred tothe second treating chamber 18 through the exchange conduit 20 and thecontrol valves 22 and a wash step of the wash cycle may be implementedin the second treating chamber 18 at 210.

If the usefulness of the treating liquid is not determined to besufficiently useful at 208, the treating liquid in the first treatingchamber 18 may be drained from dishwasher 10 by the drain pump 40 at212. Further, fresh or new treating liquid may be provided directly tothe second treating chamber 18 to implement a wash step according to thewash cycle for the second treating chamber 18.

From either 210 or 212, after the wash step in the second treatingchamber 18 is complete, the controller 60 may make a determination at214 if the wash step just completed in the second treating chamber 18 isthe last step to be completed in both wash cycles for the first andsecond treating chambers 18. If the wash step just completed in thesecond treating chamber 18 at 210 or 212 is not the last step in bothwash cycles, a next cycle step may be implemented at 216, and steps 204to 214 of the method 200 may be repeated until it is determined at 214that the wash cycles are complete at 218.

While the method 200 illustrates one example of operating the dishwasher10, other examples of operating a dishwasher in accordance with theinvention may be also possible. For example, the sequence of thewash/rinse steps in a wash cycle may be modified by the frequency ofmonitoring of the soil load. The following alternative examples of themethod 200 assume that the dishwasher 10 has two treating chambers 18:

Example 1

The method 200 can be performed without checking the usefulness of thetreating liquid at 206. Rather, the treating liquid may be transferredalternatively between the two treating chambers 18 until the wash and/orrinse steps of both wash cycles are complete, such that the operation ofthe dishwasher 10 may be performed in the order of first treatingchamber, second treating chamber, first treating chamber, secondtreating chamber, etc.

Example 2

The method 200 can include determining the treating chamber 18 with thelightest soil load multiple times during the wash cycles for the twotreating chambers 18. The soil load of the treating chambers 18 may bemonitored, such as by the turbidity sensor, multiple times during theirrespective wash cycles, for example, to determine which treating chamber18 has the lightest soil load at the end of each wash step and/or rinsestep of the wash cycle. For example, upon completion of a wash step inthe first treating chamber 18 having the lightest soil load, thetreating liquid may be transferred to the second treating chamber 18having a heavier soil load for completion of a wash step. The increasein the soil load for each treating chamber 18 during the wash step maybe monitored using sensors, such as by the increase in turbidity. Thetreating liquid may then next be used in the treating chamber 18 havingthe least soil load increase during the wash step. In other words, ifthe soil load increase in the first treating chamber 18 is less than thesecond treating chamber 18, the treating liquid may be transferred tothe first treating chamber 18. If the soil load increase in the secondtreating chamber 18 is less than the first treating chamber 18, thetreating liquid may remain in the second treating chamber 18 toimplement next wash step or rinse step. A series of determining stepsmay iterate to determine where the treating liquid should be used tobest retain the usefulness of the treating liquid until the wash cyclesare completed for both treating chambers 18. It is noted that thedetermining steps may be selectively implemented during a cycle ofoperation.

FIG. 3 is a flow chart showing a method 300 of operating the dishwasher10 of FIG. 1 according to a second embodiment of the invention. Ingeneral, the method 300 is directed to using controlled amount oftreating chemistry in the dishwasher 10 to minimize any potential damageto the utensils in the treating chambers 18 from too much treatingchemistry. The sequence of steps depicted in method 300 is forillustrative purposes only, and is not meant to limit the method 300 inany way as it is understood that the steps may proceed in a differentlogical order or additional or intervening steps may be included withoutdetracting from the invention. The method 300 may be implementedindependently or as a part of a wash, such as a pre-wash, wash, rinse,or dry phase. The method 300 assumes that the dishwasher 10 includes twotreating chambers 18, and also assumes that utensils are provided toeach treating chamber 18 for treatment. The method 300 further assumesthat one treating chamber 18 is to be provided with treating liquidfirst to implement a wash cycle; for the purposes of the description ofthe method 300, this treating chamber 18 will be referred to as thefirst treating chamber 18 and the other treating chamber 18 will bereferred to as the second treating chamber 18.

At 302, treating liquid that includes a treating chemistry is suppliedto the first treating chamber 18. The treating liquid may include amixture of water and the treating chemistry, such as a detergent-watersolution. The supply of treating liquid may be done as part of a washstep in a wash cycle. The treating liquid can be sprayed onto theutensils in the utensil rack 28 from the spray arm assembly 32. Thetreating liquid may be recirculated through the treating chamber 18 oneor more times by the recirculation pump 38. Treating chemistry can bedispensed from the chemistry dispenser 48.

At 304, a determination is made as to whether the treating chemistry inthe treating liquid used for the first treating chamber 18 at 302 issuitable to use in the second treating chamber 18. For example, theamount or concentration of detergent used for the first treatingchamber, such as when running a Heavy Duty cycle, may be great enough tochemically mark the utensils in the second treating chamber, such whenrunning a China cycle. The risk of chemical marking may be exacerbatedif the treating chemistry in the chemistry dispenser 48 for the secondtreating chamber 18 is released and further increases the amount orconcentration of the treating chemistry in the liquid from the firsttreating chamber 18. The determination at 304 aids in identifying thispossible risk. The determination at 304 may be based on the type oftreating chemistry, the amount of treating chemistry, the concentrationof treating chemistry, and/or the pH of the treating liquid. One or moresensors coupled to the chemistry dispenser 48 or the sump 36 of thefirst treating chamber 18 may send an output signal to the controller 60indicating the type and/or pH of the treating chemistry. Alternatively,the type of treating chemistry may be identified by the user based onindicia on a cartridge holding the treating chemistry in the chemistrydispenser 48 and inputted via the user interface 62. Alternatively, thecontroller 60 may be configured to detect the cartridge and determinethe type of treating chemistry from the cartridge.

If the treating chemistry in the first treating chamber 18 is notsuitable for use in the second treating chamber 18, the treating liquidmay be drained at 306. Fresh or new treating liquid may be supplied tothe second treating chamber 18 before implementing a wash step in thesecond treating chamber 18.

If the treating chemistry in the first treating chamber 18 is suitablefor use in the second treating chamber 18, the treating liquid may betransferred from the first treating chamber 18 to the second treatingchamber 18 at 308.

Upon transferring the liquid to the second treating chamber 18, it maybe determined at 310 if the addition of more treating chemistry, such asany treating chemistry stored in the chemistry dispenser 48 of thesecond treating chamber 18, to the treating liquid would result indamage to the utensils in the second treating chemistry. Treatingchemistry such as detergent may have high pH, which may be a source ofchemical-attack, such as chemical marking, on and etching of utensils,especially utensils comprising glass, such as some cups or china. Therate of etching or marking may be accelerated when combined with anincreased temperature, such as a hot water wash and/or rinse step duringthe wash cycle. Therefore, etching may be reduced by dispensing anoptimum amount of treating chemistry to the second treating chamber 18.

The determination at 310 may be based both on the amount of treatingchemistry in the chemistry dispenser 48 of the second treating chamber18, the amount of treating chemistry in the treating liquid from thefirst treating chamber 18, and information specific to the load ofutensils in the second treating chamber 18. The amount of the treatingchemistry in the dispenser 48 of the second treating chamber 18 may beknown from the dose size of the chemistry dispenser 48. The amount ofthe treating chemistry in the treating liquid from the first treatingchamber 18 may be known from the dose size of the chemistry dispenser 48in the first treating chamber 18 or from the wash cycle run in the firsttreating chamber 18. Alternatively, a more precise amount of treatingchemistry in the treating liquid, which may effectively participate inthe enzyme reaction with soil, may be calculated by a chemical sensor,such as the pH sensor 56 or a surface acoustic wave (SAW) sensor, in thefirst or second treating chamber 18, and an output signal correspondingto the pH or concentration of treating chemistry may be sent to thecontroller 60. Information (turbidity, soil load, etc.) specific to theload of utensils in the second treating chamber 18 may be collectedusing any of the previously described methods/sensors before or duringthe wash/rinse step. Once all of the information is collected, thecontroller 60 can run one or more algorithms to determine if adding thetreating chemistry in the chemistry dispenser 48 of the second treatingchamber 18 to the treating liquid from the first treating chamber maylikely cause damage to the utensil load in the second treating chamber18.

If it is determined that adding the treating chemistry in the chemistrydispenser 48 of the second treating chamber 18 to the treating liquid isnot likely to cause damage to the utensils, the treating chemistry inthe chemistry dispenser 48 may be provided to the treating liquid at312.

If it is determined that adding the treating chemistry in the chemistrydispenser 48 of the second treating chamber 18 to the treating liquid islikely to cause damage to the utensils, it is determined at 314 if thetreating chemistry in the chemistry dispenser 48 of the second treatingchamber 18 can be dispensed in a subsequent wash and/or rinse step. Forexample, it can be determined at 314 if the treating chemistry in thechemistry dispenser 48 is needed for a subsequent wash step in either ofthe treating chambers 18. The determination may be based on a comparisonof the wash cycles for the two treating chambers 18.

If the additional treating chemistry is determined to be useable in atleast one of the treating chambers 18, it is determined at 316 if theadditional treating chemistry may be used in the second treating chamber18. Again, the determination may be based on a comparison of the washcycles for the two treating chambers 18. If it is determined that theadditional treating chemistry may be used in a subsequent wash step inthe second treating chamber 18, at 318 the additional treating chemistrymay be held in the chemistry dispenser 48 of the second treating chamber18 for later use. For example, the dispensing cartridge in the chemistrydispenser 48 of the second treating chamber 18 may store and hold thetreating chemistry until the treating chemistry may be dispensed in thesubsequent wash step.

If it is determined at 316 that the additional treating chemistry willbe used in the first treating chamber 18, the treating chemistry may beadded to treating liquid in the second treating chamber 18 before beingtransferred to the first treating chamber 18 in 320. This may be delayeduntil the dishwasher is ready to commence the wash step in the firsttreating chamber 18. In this case, the second treating chamber 18 may beemptied before supplying fresh or new water and adding the treatingchemistry from the chemistry dispenser 48. Otherwise, the treatingchemistry can be added to existing treating liquid in the secondtreating chamber. Therefore the wash step in the first treating chamber18 may be postponed until the wash step in the second treating chamber18 is completed.

If it is determined at 314 that the treating chemistry in the chemistrydispenser 48 of the second treating chamber 18 cannot be used in asubsequent wash step in either treating chamber 18, it may then bedetermined at 322 whether if the treating chemistry can be used in thesecond treating chamber 18 in a subsequent wash cycle. A subsequent washcycle may be implemented in the second treating chamber 18 after a shortperiod of time, such as less than one hour, or after an extended periodof time, such as in couple days, depending on the user. If the userplans to dispense and use the treating chemistry in a subsequent washcycle, the treating chemistry may be stored in the chemistry dispenser48 for later use at 324. However, if a cycle of operation is not to beimplemented for an extended time period, for example, a month, thetreating chemistry may be dispensed to the second treating chamber 18and drained from the dishwasher 10 at 326. In making the determinationat 322 whether the additional treating chemistry can be held for lateruse at 324 or drained at 326, other parameters such as the effect ofhumidity on the treating chemistry and frequency of dishwasher operationmay be considered by the controller 60.

FIG. 4 is a schematic, perspective view of a second exemplary dishwasher400 having multiple treating chambers in the form of a drawer-typedishwasher 400. The methods 200, 300 disclosed herein may be carried outby the dishwasher 400. As illustrated, the dishwasher 400 may include asingle cabinet and two wash tubs 416, such as an upper wash tub 416 anda lower wash tub 416, each at least partially defining a treatingchamber 418. Each wash tub 416 can be at least partially defined by adrawer 417 slidably supported within the cabinet 412 for movementbetween an open position, shown, and a closed position, not shown. It isnoted that the dishwasher 400 may include one or more components notshown in FIG. 4. For example, each of the treating chambers 418 may beprovided with a liquid supply system and controller similar to thosedescribed above for FIG. 1. The two treating chambers 418 are fluidconnected to each other to selectively transfer liquid between the twotreating chambers 418.

The invention described herein provides methods for operating adishwasher having multiple treating chambers. The methods of theinvention can advantageously be used to reuse treating liquid in anotherwash step or optimize the dose of treating chemistry for the utensils ineach treating chamber.

While the invention has been specifically described in connection withcertain specific embodiments thereof, it is to be understood that thisis by way of illustration and not of limitation. Reasonable variationand modification are possible within the scope of the forgoingdisclosure and drawings without departing from the spirit of theinvention which is defined in the appended claims.

What is claimed is:
 1. In a dish washing system having at least two,independently-operable treating chambers, each having a user-filleddetergent cup, and in each of which separate user-selected wash cyclesare implemented, a method of sharing a wash liquid comprising a solutionof detergent and water between the treating chambers during theimplementation of the wash cycles, comprising: a) determining that adetergent concentration of the wash liquid in one of the wash cycles isbelow a detergent concentration threshold for an other of the washcycles; and b) supplying the wash liquid to an other treating chamber inwhich the other of the wash cycles is implemented, for use in the otherof the wash cycles, when the detergent concentration of the wash liquidis below the detergent concentration threshold.
 2. The method of claim 1wherein the determining whether a detergent concentration of the washliquid in the one of the wash cycles satisfies the detergentconcentration threshold for the other of the wash cycles comprisesdetermining the detergent concentration of the wash liquid in the one ofthe wash cycles based on a user selected cycle information.
 3. Themethod of claim 1, further comprising confirming the detergentconcentration of the wash liquid by utilizing a sensor selected from thegroup consisting of: a pH sensor, a turbidity sensor, and a chemicalsensor.
 4. The method of claim 1, further comprising dispensingdetergent from the detergent cup of the other treating chamber in whichthe other of the wash cycles is implemented.
 5. The method of claim 4wherein the dispensing is delayed for a predetermined time.
 6. Themethod of claim 5 wherein the predetermined time is set such that acleaning action of the wash liquid remains below a predeterminedthreshold and is determined based on at least one of: concentration ofdetergent in the wash liquid, temperature of the wash liquid, pH of thewash liquid, water hardness, and soil level of utensils in the othertreating chamber.
 7. The method of claim 6 wherein the cleaning actionof the wash liquid is determined using at least one of: a pH sensor, aturbidity sensor, a temperature sensor, a timing sensor, and aconductivity sensor.
 8. The method of claim 1, further comprisingrefraining from dispensing detergent from the detergent cup of the othertreating chamber in which the other of the wash cycles is implementeduntil the wash liquid is drained from the other treating chamber.
 9. Themethod of claim 8, further comprising removing the dispensed detergentfrom the other treating chamber in which the other of the wash cycles isimplemented.
 10. The method of claim 9 wherein the removing thedispensed detergent comprises draining the dispensed detergent from theother treating chamber in which the other of the wash cycles isimplemented.
 11. The method of claim 1 wherein the dish washing systemfurther comprises a common chassis and the at least two,independently-operable treating chambers are provided within the commonchassis.